Abstract: According to established routes for the microporous metallization of printed circuit boards (PCB), electroless copper plating using glyoxylic acid as a reducing agent and copper electroplating in a citrate bath were used for microporous metallization with PCB distributing micropores as a template. The results show that electroless copper plating using glyoxylic acid as a reducing agent and copper electroplating in a citrate bath can be successfully applied to the microporous metallization of PCB. After an electric conducting treatment of the micropores by electroless copper plating the copper deposited as fine grains and attached to the inner walls of the micropores. The copper deposit was also found in the loose grain arrangement and the leak plating area. Immediately after thickening treatment by copper electroplating, the resistance toward the copper coating of the inner wall decreased notably. The ratio of the copper electroplating rates at the inner and outer micropores was found to be 0.8:1.0. The copper electrodeposit fully covered the surface of the inner wall including the leak plating area, which means that the electroplated copper grains have a certain sideway growing ability. The copper coating on the inner wall was continuous, compact, and adhesive. This coating highly enhanced the conductivity of the interconnected PCB.

Key words: Micropore, Electroless copper plating, Copper electroplating, Metallization, Printed circuit board